Delay? Cockney bloke’s on time! (5)
I believe the answer is:
tarry
'delay?' is the definition.
(to tarry is to delay leaving a place)
'cockney bloke's on time' is the wordplay.
'cockney bloke' becomes ''arry' ('Harry' - common masculine name - said with a cockney accent, dropping the 'H').
'on' means one lot of letters go next to another.
'time' becomes 't' (abbreviation).
'arry' put after 't' is 'TARRY'.
(Other definitions for tarry that I've seen before include "perhaps not to split" , "Drag one's feet" , "Wait" , "Famous novel by Patrick Kavanagh - '. . . . . Flynn'" , "Hot and sticky" .)